994
FXUS65 KBOI 272007
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
207 PM MDT Tue Oct 27 2026

.KEY MESSAGES...
- Isolated to scattered showers today, greatest coverage
  northern mountain zones. minor snow accumulations above 6000
  ft MSL.

- Gradual clearing this evening. With temperatures around 5
  degrees below normal through Wednesday.

- Dry and warmer Thursday, precipitation chances increasing
  Friday into the weekend.

&&

.SHORT TERM /Through Thursday Night/...
A weak shortwave disturbance will track across the region this
afternoon and evening, generating isolated showers mainly over
higher terrain and northern mountain zones. Precipitation
amounts will remain light. Any lingering shower activity will
diminish rapidly late this evening with the departure of the
shortwave.

Skies will clear tonight behind the exiting disturbance,
promoting efficient radiational cooling. Low temperatures
Wednesday morning will dip into the lower to mid 30s across many
lower valleys, with freezing temperatures expected in higher
valleys. This will support patchy frost development Wednesday
morning.

A weak upper level ridge will build overhead Wednesday into
Thursday ahead of a deepening low pressure system off the
Pacific Northwest coast. This pattern will bring dry conditions
and a slight warming trend, with daytime high temperatures
rebounding closer to seasonal normals. Another round of patchy
to widespread frost is possible early Thursday morning across
valley locations, as mostly clear skies and light winds foster
even better radiational cooling conditions than the previous
night.

By late Thursday and Thursday night, the offshore low will dig
further south off the Pacific Northwest coast, shifting flow
aloft to a more southerly to southwesterly direction. This will
begin to advect mid and upper level moisture northeastward from
the southwestern United States into the northern Great Basin.
Ensemble guidance suggest sufficient moisture and weak lift
could trigger isolated to scattered light showers across the
central Idaho mountains late Thursday afternoon into Thursday
night, while lower elevations and southeast Oregon remain mostly
dry.

&&

.LONG TERM /Friday through Tuesday/...
Friday, a closed low off the Pacific Northwest Coast amplifies
along a southward trough axis capturing a pocket of tropical
moisture. As a deep Alaskan Low strengthens, it captures the
closed low, trough, and tropical moisture. As they move inland,
the low heads northeastward and carries the moisture and colder
air inside the trough up through the forecast area. The entire
synoptic process takes place from Friday through early Monday,
during which precipitation chances increase and
temperatures/snow levels fall. The primary cold front passes
early Sunday morning in the latest ensemble means, so the
weather Friday and Saturday feature modest precip chances
(10-40%, higher over terrain) and snow levels around 5-7 kft
MSL. Temperatures during this period hover around to just above
normal for this time of year. Halloween evening (Saturday),
precipitation chances increase sharply to 40-70% as temperatures
and snow levels begin to dip. Sunday morning snow levels drop
to 4-6 kft MSL, and by Monday they drop further to 3.5-4.5 kft
MSL. At least some snowfall is likely above 5 kft MSL, and at
least some chance of snow exists down to 4 kft MSL even though
precipitation chances begin to decrease Sunday night, limiting
how much precipitation falls when snow levels are lowest. Dry
conditions will prevail through the beginning of next week.
Seasonable or below normal temperatures will continue through
the long-term period.

&&

.AVIATION /18Z Tuesday through Wednesday/...
Issued 1123 AM MDT TUE OCT 27 2026
Mountains obscured and scattered rain and mtn snow showers are
expected through the afternoon. Low VFR to IFR in showers.
Another round of showers arrives overnight in northern mountains
near KMYL. Snow levels 5000-6000ft MSL drop to 4000-5000ft MSL
tonight. Surface winds: Variable 5-15 kt. Winds aloft at 10kft
MSL: W 10-25 kt.

KBOI...Generally VFR. Isolated rain/graupel showers will
develop this afternoon. They will stay over the foothills with a
low chance of impacting the airport. Surface winds: SE 3-8 kt
this morning, shifting to NW 3-8 kt this afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.

OR...None.

&&

$$

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SHORT TERM...JDS
LONG TERM....JM
AVIATION.....JM